The sys admin's daily grind: parallel SSH
Mass Start
Parallel SSH is the name of an easy-to-configure tool that our resident sys admin, Charly, now routinely deploys whenever he needs to launch the same programs, copy the same files, or kill the same processes simultaneously on multiple computers.
I am writing from a Linux seminar in the Linuxhotel in Essen, Germany. The environment here comprises four Xen virtualized machines. Identical changes to all cluster nodes are a regular requirement, which is a pain, but I have a utility up my sleeve: parallel SSH [1]. Pssh relies on the SSH agent running, so I'll take care of that first:
ssh-agent ssh-add
After I enter the pass phrase for my SSH key, the AAH agent ensures that nobody will ask me for it, at least not during the current session. Next, I need a text file in which I add the IP addresses of the servers for which I need to set up simultaneous connections, so I'll start by adding three addresses to server.txt:
192.168.5.12 192.168.5.52 192.168.5.67
First, I will open an SSH connection to these three computers, run the uname command on them, and redirect the output to my pssh-out directory with the command line:
pssh -h server.txt -l charly -o /home/charly/pssh-out uname
Now I have three files below /home/charly/pssh-out named after the server IP addresses. And lo and behold, the files contain the uname command output (Figure 1). Pssh is thus similar to the Distributed Shell (DSH).

Two Hard-Hitting Tools
PSCP and PNuke, which are also part of the pssh package, work along the same principle.
PSCP copies files simultaneously to multiple target machines. This command adds a new message of the day to my servers:
pscp -h server.txt -l charly /etc/motd /etc/
PNuke sends a kill -9 to identically named processes on three servers
pnuke -l server.txt -l charly wget
and terminates any wget processes running on them. This frees up some bandwidth.
Conclusions
Brilliant. The most difficult thing about the pssh suite is saying its Internet page name, theether.org, without tripping over your own tongue.
Infos
- Parallel SSH: http://www.theether.org/pssh/
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
News
-
Another New Linux Laptop has Arrived
Slimbook has released a monster of a Linux gaming laptop.
-
Mozilla VPN Now Available for Linux
The promised subscription-based VPN service from Mozilla is now available for the Linux platform.
-
Wayland and New App Menu Coming to KDE
The 2021 roadmap for the KDE desktop environment includes some exciting features and improvements.
-
Deepin 20.1 has Arrived
Debian-based Deepin 20.1 has been released with some interesting new features.
-
CloudLinux Commits Over 1 Million Dollars to CentOS Replacement
An open source, drop-in replacement for CentOS is on its way.
-
Linux Mint 20.1 Beta has Been Released
The first beta of Linux Mint, Ulyssa, is now available for downloading.
-
Manjaro Linux 20.2 has Been Unleashed
The latest iteration of Manjaro Linux has been released with a few interesting new features.
-
Patreon Project Looks to Bring Linux to Apple Silicon
Developer Hector Martin has created a patreon page to fund his work on developing a port of Linux for Apple Silicon Macs.
-
A New Chrome OS-Like Ubuntu Remix is Now Available
Ubuntu Web looks to be your Chrome OS alternative.
-
System76 Refreshes the Galago Pro Laptop
Linux hardware maker has revamped one of their most popular laptops.